The present invention relates to apparatus for extracting samples of liquid from flow lines or tanks thereof.
Various manufacturing operations require that the immediate or overall composition of a liquid flowing through a pipe or conduit be monitored or determined. Such monitoring ordinarily is accomplished with apparatus, sometimes denoted as samplers, which take samples of liquid from the main body thereof. Where a composite sample of the liquid flow is required, the sampler is usually operated to withdraw a series of small, measured amounts of the liquid as it passes a sampling point. The individual samples are collected, and represent a composite sample of the total volume of liquid.
One instance in which composite sampling is used, for example, is in determining the fat content of milk. Milk received by a dairy from individual dairy farmers is pumped into a large storage tank. Since the batches of milk supplied by the individual dairy farmers ordinarily differ in fat content, stratified layers of milk of various fat content are formed in the tank. To determine the overall fat content of the milk in the tank, the milk could be thoroughly stirred and then sampled, but this is expensive and time consuming. Instead, as the milk is removed from the tank through a conduit it is advantageous to periodically extract and collect discrete and measured amounts of milk from the conduit to obtain a composite sample of the milk in the tank. The sample may then be analyzed for fat content, which represents the overall fat content of the milk.
Other uses for samplers are in on-line analysis applications in which the immediate composition of a liquid must be determined. For this application, the individual samples of liquid are not collected as a composite sample, but instead are separately analyzed.
To obtain the samples, some samplers continuously divert streams of liquid from the flow lines or tanks, and from the diverted streams the samples are removed in various ways. Attempts to withdraw small measured quantities directly from the pipes or tanks, however, have presented many problems not satisfactorily solved. For example, liquid receiving holes or slots in samplers adapted to be extended directly into a pipe require an orienting mechanism, and the sampled material often builds up in such holes and slots and either blocks the same or contaminates subsequent samples. Such samplers obviously cannot be used where a high degree of sanitation is required, such as in the sampling of food products, and are ill suited to handle high viscosity or thixotropic liquids. In addition, conventional samplers are difficult to disassemble for inspection, cleaning and replacement of parts, and excessive leakage and clogging of the samplers are problems common to many types of samplers.